U.S. patent number 4,891,633 [Application Number 06/633,587] was granted by the patent office on 1990-01-02 for digital image exchange system.
This patent grant is currently assigned to General Research of Electronics, Inc.. Invention is credited to Kazuyoshi Imazeki, Yasuo Nagazumi.
United States Patent |
4,891,633 |
Imazeki , et al. |
January 2, 1990 |
Digital image exchange system
Abstract
A digital image exchange system comprises a data transmission
line, at least one video RAM, at least one video signal generator
for accessing data from the video RAM and for developing at least
two video signals corresponding respectively to the accessed data,
and at least one modulator for modulating the video signals to form
transmitted signals in at least two different frequency bands to be
transmitted on the data transmission line. At least one demodulator
is coupled to the transmission line at a location remote from the
modulator for demodulating the transmitted signals in each of the
at least two frequency bands to form at least two corresponding
video signals; and at least one video display device is operatively
coupled with the demodulator for displaying visual images
corresponding to the respective video signals.
Inventors: |
Imazeki; Kazuyoshi (Tokyo,
JP), Nagazumi; Yasuo (Tokyo, JP) |
Assignee: |
General Research of Electronics,
Inc. (Tokyo, JP)
|
Family
ID: |
24540253 |
Appl.
No.: |
06/633,587 |
Filed: |
July 23, 1984 |
Current U.S.
Class: |
345/2.1;
348/E7.076; 358/425; 370/489; 380/34; 725/118; 725/74 |
Current CPC
Class: |
H04N
1/001 (20130101); H04N 1/2179 (20130101); H04N
7/17363 (20130101); H04N 2007/1739 (20130101) |
Current International
Class: |
H04N
1/21 (20060101); H04N 7/173 (20060101); H04N
1/00 (20060101); H04K 001/00 () |
Field of
Search: |
;358/86,259,85,102,903
;340/825.52,706,717 ;364/900,200 ;380/34,3-5,249-250,18
;370/69.1,85,88,124 ;379/53,54,110 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Buczinski; Stphen C.
Assistant Examiner: Gregory; Bernarr Earl
Attorney, Agent or Firm: Backstone, Jr.; R. A.
Claims
The invention is claimed as follows:
1. A digital image exchange system comprising: a single
bidirectional data transmission line for exchanging digital images;
video RAM means; video signal generator means for accessing data
from said video RAM means and for developing at least two video
signals corresponding respectively to the accessed data; a
plurality of modulator means for modulating said video signals to
form transmitted signals in at least two different frequency bands
to be transmitted on said data transmission line; a plurality of
demodulator means coupled to said transmission line at a location
remote from said modulator means for demodulating said transmitted
signals in each of said at least two frequency bands to form at
least two corresponding video signals; and at least one video
display device operatively coupled with said each of said
demodulator means for displaying visual images corresponding to the
respective video signals.
2. The system of claim 1, and further comprising at least one
additional source of video signals, and combining means coupled to
said demodulator means and to said at least one additional source
for combining a first one of said at least two video signals with
one of a second one of said at least two video signals and a video
signal from said additional source of video signals.
3. The system of claim 1, and further comprising scrambling means
coupled with said video signal generator means for encoding said
video signals generated by said video signal generator means to
form encoded signals; and descrambling means coupled with said
demodulator means for decoding said encoded signals.
4. The system of claim 1 and further comprising video signal
digitalizer means connected between said demodulator means and said
video display device for converting video signals into digital
data.
5. The system of claim 1, wherein said data transmission line
comprises a transmission medium of a local-area network
communication system.
6. The system of claim 1 wherein said video RAM means comprises a
plurality of video RAM's and wherein said video signal generator
means comprises a plurality of video signal generators for
separately accessing data from respective ones of said plurality of
video RAM's.
7. A system according to claim 6 wherein said plurality of video
RAM's are remotely located with respect to said video display
device; and further including at least one local video RAM
operatively coupled with said demodulator means and with said at
least one video display device.
8. A system according to claim 1 wherein said video RAM means
comprises a single video RAM and wherein said video signal
generator means comprises a plurality of video signal generators
for separately accessing data from a plurality of different,
preselected portions of said video RAM.
9. A system according to claim 8 and further including at least one
local video RAM operatively coupled with said demodulator and with
said at least one video display device.
10. A digital image exchange system comprising: a host computer
system; a plurality of work stations located remotely from said
host computer system; and a single data transmission line means
bidirectional coupling said host computer system with said
plurality of work stations; said host computer system including
video RAM means, video signal generator means for accessing data
from said video RAM means and for developing at least two video
signals corresponding respectively to the accessed data, and a
plurality of modulator means for modulating said video signals to
form transmitted signals in at least two different frequency bands
to be transmitted on said data transmission line; each of said work
stations comprising demodulator means coupled to said transmission
line for demodulating said signals in each of said at least two
frequency bands to form at least two corresponding video signals,
and video display means operatively coupled with said demodulator
means for displaying visual images corresponding to the respective
demodulated video signals.
11. The system of claim 10 wherein said video RAM means comprises a
single video RAM and wherein said video signal generator means
comprises a plurality of video signal generators for separately
accessing data from different, preselected portions of said video
RAM means.
12. A system according to claim 10 wherein said host computer
system includes a host computer and wherein each of said work
stations includes a work station computer, and further including
network bus means for coupling said host computer with said work
station computers to form a computer network.
13. A system according to claim 12 wherein each of said work
station computers is responsive to said host computer for
controlling transmission of demodulated video images from its
associated demodulator means to its associated video display
means.
14. A system according to claim 13 wherein said host computer
system includes a host computer and wherein each of said work
stations includes a work station computer and further including
network bus means coupled intermediate said host computer and said
work station computers to form a computer network.
15. A system according to claim 14 wherein said demodulator means
comprises a plurality of demodulators, and wherein said video
display means comprises a plurality of video display devices
respectively operatively coupled with selected ones of said
plurality of demodulators, and further including control means
responsive to said host computer for controlling transmission of
demodulated video signals between selected ones of said
demodulators and the associated video display devices.
16. A system according to claim 12 wherein said network bus means
and said data transmission line means comprise the transmission
medium of a local-area network communication system.
17. The system according to claim 16 and further comprising a
plurality of similar host computer systems coupled with said
network bus means and with said data transmission line means.
18. A system according to claim 10 wherein at least one of said
work stations further includes local video RAM means operatively
coupled with said video display means and with said demodulator
means.
19. A system according to claim 18 wherein said work station
computer of said at least one work station is coupled to said local
video RAM for selective local modification of the video image
data.
20. A digital image exchange system comprising a host computer
system; a plurality of work stations remote from said host computer
system; at least one display station located remotely from said
host computer system and from said plurality of work stations, and
a single bidirectional data transmission line means for exchanging
digital images; said host computer system and each of said work
stations including video RAM means, video signal generating means
for accessing data from said video RAM means and for developing
video signals corresponding to the accessed data, and modulator
means for modulating said video signals to form transmitted signals
in a given frequency band to be transmitted on said data
transmission line, each of said host computer and said plurality of
work stations transmitting said transmitted signals in a different
frequency band; said display station including a plurality of
demodulator means coupled to said data transmission line means for
demodulating the transmitted signals in each of said frequency
bands to form corresponding video signals, and video display means
operatively coupled with said demodulator means for displaying
visual images corresponding to the respective demodulated video
signals.
21. A system according to claim 20 wherein said display station
further includes at least one local video RAM coupled with said
demodulator means and with said video display means.
Description
BACKGROUND OF THE INVENTION
The invention relates generally to visual image display systems and
more particularly to a high speed digital image exchange system
which supports a plurality of display devices for one or more
computers, video terminals or graphic work stations.
The transmission of visual images or visual pattern data often
requires considerable time because of the limited data-transmission
speed normally possible over a conventional transmission line. For
example, a typical video random access memory (VRAM) capable of
storing one frame of video information comprising 512 .times.512
piccels having 4096 colors, must leave a storage capacity of about
3Mbits/frame. Transmitting 3Mbits (i.e., 3.times.10.sup.6 bits) of
information would require about 5.5 minutes over a RS232C serial
line which has 9600 bands transmission capacity, for example. Such
a long transmission time is too long for an interactive operation
system of a computer.
It is possible to improve transmission time by connecting each
video terminal to a remote processor. However, this necessitates
very complicated wiring and requires that strict limitations on
cable lengths be observed, because of signal attenuation
characteristics of cable. Furthermore, signal source selection is
also greatly restricted, because of the need for physical cable
switching or reconnection to accommodate selection from among
multiple sources.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
digital image exchange system with increased data transmission
speed on a simple transmission line, for example, a broad band
coaxial cable.
It is a further object to provide a digital image exchanger system
with improved access to multiple source areas in a video RAM
device.
It is a further object to provide a digital image exchange system
which can operate on the same transmission line used by a
local-area network (LAN) system, in frequency-separated
channels.
It is a further object to provide a digital image exchange system
with improved security features for limiting access to information
in the system to authorized persons.
A digital image exchange system comprises a data transmission line;
video RAM means; video signal generator means for accessing data
from said video RAM means and for developing at least two video
signals corresponding respectively to the accessed data; and
modulator means for modulating said video signals to form
transmitted signals in at least two different frequency bands to be
transmitted on said data transmission line. Demodulator means are
coupled to said transmission line at a location remote from said
modulator means for demodulating said transmitted signals in each
of said at least two frequency bands to form at least two
corresponding video signals; and at least one video display device
is operatively coupled with said demodulator means for displaying
visual images corresponding to the respective video signals.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention which are believed to be
novel are set forth with particularity in the appended claims. The
organization and manner of operation of the invention, together
with further objects and advantages thereof, may best be understood
by reference to the following description taken in connection with
the accompanying drawing which like reference numerals identify
like elements, and in which:
FIG. 1 is a block diagram of a first embodiment of digital image
exchange system in accordance with the invention;
FIG. 2 is a block diagram of a second embodiment of a digital image
exchange system, similar to FIG. 1 and adapted for use in a
computer assisted design system;
FIG. 3 is a diagrammatic view of an operator terminal which may be
used in conjunction with the system of FIG. 2; and
FIG. 4 is a block diagram of a further embodiment of a digital
image exchange system similar to the system of FIG. 2.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
Referring to FIG. 1, there is illustrated a block diagram of a
digital image exchange system or communications network 100 in
accordance with the present invention in conjunction with a system
comprising a plurality of similar small computers 10a, 10b . . .
10n which are coupled to a network bus 11 to operate as a computer
network. A plurality of video random access memories (VRAM's) 12a,
12'a and 12b . . . 12n are coupled to computers 10a and 10b . . .
10n, respectively.
A corresponding plurality of video signal generators 14a, 14'a and
14b . . . 14n respectively access these VRAM's by way of
corresponding direct memory access devices (DMA's) 16a, 16'a and
16b . . . 16n and provide video signals to corresponding modulators
18a, 18'a and 18b . . . 18n, respectively. Each modulator operates
to modulate the video signals to a predetermined frequency range or
band or "channel". These modulated signals are then combined to
form transmitted signals on a data transmission line such as a
coaxial cable or trunk 20. The computers 10b . . . 10n may also be
provided with video displays such as cathode ray tubes (CRT's) 17b
. . . 17n to display video information from the corresponding
VRAM's 12b . . . 12n by way of the DMA's 16b . . . 16n.
The operation of each of the video signal generators 14a, 14b . . .
14n may be under control of the associated one of computers 10a,
10b . . . 10n. Similarly, the contents of each of the VRAM's are
controlled by the associated one of the computers.
A display station or portion 21 may be at a location remote from
the computer network and includes a plurality of demodulators 22,
24, 26 and 28. These demodulators receive the modulated and
transmitted signals in the predetermined frequency bands from the
coaxial cable 20 and convert these signals back into corresponding
video signals. In the example illustrated in FIG. 1, demodulator 26
is connected directly to a video display such as a cathode ray tube
(CRT) 30 to display the transmitted and demodulated image. The
output signals from demodulators 22 and 24 are fed to a second CRT
32 through a switching device 34 which, under the control of the
computer 10a, selects either the signal from one of the
demodulators 22, 24 or the signal from the video signal generator
14a and displays the corresponding video image.
The output signal from demodulator 28 is fed to a video signal
digitalizer 36 which converts the video signal into digital codes
and stores them in another, local VRAM 38. An additional video
signal generator 40 accesses this local VRAM 38 independently by
way of a DMA 41 and generates video signals to display on a further
associated CRT 42. The video signal digitalizer 36 is also
controlled by the computer 10a.
Advantageously, when using the system described above, the capacity
of single transmission line such as cable or channel 20 is utilized
more efficiently because the cable or channel is no longer
dedicated to a single modulator and a single demodulator. The
system described above is particularly useful for monitoring and
controlling a plurality of computers with a single, relatively
small computer of relatively low data communication capacity and
performance. This is possible because the whole system can be
monitored from a controlling unit such as the computer 10a. For
example, any system defect or unauthorized operation of the various
elements of the system may be visually monitored.
In the foregoing example, the switching device 34 may be replaced
by a video signal mixing device. This latter alternative allows
cumulative video images to be generated by combining the output
signals from two or more of the VRAM's.
It will be understood that computer 10a and associated components
in the foregoing example form as a host or controlling computer
system 44 with respect to the display station or portion 21 and the
remaining computers 10b . . . 10n. In this regard, computers 10b .
. . 10n and the respective related components may be remotely
located with respect to host computer system 44, to form work
stations or remote terminals 46a . . . 46n.
Referring to FIG. 2, there is illustrated a block diagram of a
digital image exchange system or communications network 200 in
accordance with the present invention embodied as a computer
assisted design (CAD) system. This system 200 contains a plurality
of graphic work stations 50a . . . 50n connected to a host computer
system 51 by use of a local-area communicator network (LAN), here
represented by a network bus 53. In this regard, personal computers
or terminals 54a . . . 54n are connected by the bus 53 to a host
computer 52, which is provided with a relatively large capacity
VRAM 58, and also accesses a data base 59. The terminals 50a . . .
50n may independently access the host computer 52 to order jobs or
the like.
The host computer 52 can directly access VRAM 58 so that the
contents of VRAM 58 are controlled by this host computer 52. The
VRAM 58 is also connected to a plurality of direct memory access
(DMA) devices 60a, 60b . . . 60n, each of which can independently
access a preselected, corresponding portion or area 58a, 58b . . .
58n of the VRAM, this pre-selection being accomplished by the host
computer 52.
The DMA devices 60a . . . 60n transmit digital data to respective
corresponding video signal generators 62a, 62b . . . 62n, which in
turn have their output signals modulated to a corresponding one of
a plurality of channels or frequency ranges or bands by
corresponding modulators 64a, 64b . . . 64n. This substantially
avoids cross-talk or interference between video signal generators.
The modulators transmit the modulated signals over a common
transmission line 66, to form a combined transmitted signal.
Demodulators 69, 70, 72, 74 and a channel selector 76 demodulate
corresponding frequency bands or channels from the combined signals
carried on the transmission line 66 and convert them back into the
corresponding video signals. At host computer system 51,
demodulator 69 feeds signals from a selected channel to be
redigitalized by a video signal digitalizer 71. This digitalized
signal may then be stored in a preselected location in VRAM 58 by a
DMA 73.
At terminal or work station 50a, the demodulated output signals
from demodulator 70 are combined at a summing amplifier 80 with the
output video signal of personal computer 54a for display on a CRT
78a. In the illustrated embodiment the video signal output of
personal computer 54a corresponds to the movement of a light pen
52.
At terminal or work station 50n, the demodulated output signals of
the demodulator 72 are redigitalized by a video signal digitalizer
84 and stored in a local VRAM 86, so that local modification of the
image data becomes possible. This data from VRAM 86 may be
displayed on an associated CRT 78n. Channel selector 76 and
demodulator 74 demodulate further specific channels or frequency
bands from the combined signals on the transmission line 66. These
demodulated signals are combined at a summing amplifier 88 into a
composite video signal for display on an associated CRT 78'n.
The system illustrated in FIG. 2 provides surprisingly flexible and
convenient computer graphic work stations. For example, the
described structure of work station 50a allows real time
inter-active operation of the host computer 52. Furthermore, the
described host computer system 51, under control of computer 52,
permits rapid selection of data from among the many portions or
areas of the VRAM 58. As a further example, the described structure
of work station 50n provides the functions of local modification of
video image and image overlay of multiple video image data, which
results in improved quality of the image displayed. The two CRT's
78n and 78'n also provide simultaneous multiple displays, which is
particularly advantageous in a CAD system, allowing the operator to
view multiple images and/or data simultaneously.
FIG. 3 illustrates an exemplary work station 50'n employing
structure similar to that described with reference to work station
50n of FIG. 2. Using such features an operator can simultaneously
make available many images such as charts or the like related to a
specific job, greatly improving operator efficiency. The
illustrated system is particularly useful fro CAD-like integrated
circuit development and image processing for remotely generated
geographical or location data related to integrated circuit
layout.
A network 300 shown in FIG. 4 is similar to network 200 of FIG. 2
and like reference numerals designate like components. In FIG. 4,
the medium for digital image transmission is a coaxial cable 94,
preferably of the type used for broadband LAN systems, and for
transmission in a frequency band separated from the band used for
image data. Signal scramblers 96 are provide for encoding the image
signals in the transmitter (i.e., host computer system) side of the
transmission line 66. Accordingly, complementary descramblers 98
are provided at the work stations 50a . . . 50n in order to recover
the image signals on the receiver (i.e., work station) side. Modems
94, 95 are respectively provided for host computer 52 and each work
station computer 54a . . . 54n to interface with the transmission
line 66. In the embodiment of FIG. 4, a plurality of similar host
computer systems 51a . . . 51n may be provided. Also additional
video signal sources such as a camera 102, a video tape recorder
(VTR) 104 and a video disc player 106 may be provided. These
additional video signal sources all feed into a selected host
system 51a . . . 51n by way of video signal digitalizer 71.
While particular embodiments of the invention have been shown and
described in detail, it will be obvious to those skilled in the art
that changes and modifications of the present invention, in its
various aspects, may be made without departing from the invention
in its broader aspects, some of which changes and modifications
being matters of routine engineering or design, and others being
apparent only after study. As such, the scope of the invention
should not be limited by the particular embodiment and specific
construction described herein but should be defined by the appended
claims and equivalents thereof. Accordingly, the aim in the
appended claims is to cover all such changes and modifications as
fall within the true spirit and scope of the invention.
* * * * *